if you have decent strength,a car to visit thrift shops,,old dogs made
by sears,whirlpool,may be 50 years old but still run well,usually the accordion folding plastic has cracked & has holes,remove it all,the top lip has a built in metal track for the window sash to hold it in place,cut masonite or 3/8 in plywood to fit snug betw ac,& the side tracks,,of both the inside lower sash & outside storm wdw track,make sure the air vents all outside,coat the plywood with linseed oil so the outside facing plywd beads water off in rain.
use duck tape to seal all outside seams, or caulk,
older acs usually can be cleaned with garden hoses,and mild soap,get the coils too,tip the unit so all water empties out,dry in sun.
use paper towel as the inside coil blades covering to filter out dirt & dust.
the cleaner the guts are on the unit,the nicer smelling the machine's air will be.